Gas-operated rock-drilling engine.



No. 896,777. PATENTED AUG. 25, 1908.

- "R. s. TROTT.

GAS OPERATED BOOK DRILLING ENGINE.

APPLICATION FILED DEO.26,1906. RENEWED FEB. 15, 1908.

4 SHEETSSHEET 1 M0. 6,777. PATENTED AUG. 25, 1908.

' R s. TROTT.

GAS OPERATED ROGK DRILLING ENGINE.

APPLIOATION FILED DEO.26,1906. RENEWED FEB.15,1908.

4 SHEETS-SHEET 2v Q fleecwcyii a No. 896,777. 3 PATENTED AUG. 25, 1908 R. s. TROTT. I GAS OPERATED ROCK DRILLING ENGINE.

APPLICATION FILED DEC. 26, 1906. RENEWED FEB. 15, 1908.

4 SHEETS-SHEET 4.

UNITED STATES PATENT OFElO-Efl,

ROLLAND smnorr, OF DENVER, COLORADO.

GAS-OPERATED ROCK-DRILLING- ENGINE,

Specification of Letters Patent.

Patented Aug. 25, 1908.

Application filed December 26, 1906, Serial No. 349,386. Renewed February 15, 1308. Serial No. 416,110.

To all 107mm it may concern.

Be it known that I, ROLLAND S. TROTT, a citizen of the United States Of America, residing in the city and county of Denver and State of Colorado, have invented a new and useful Gas-Operated Rock-Drilling Engine, of which the following isa specification.

My invention relates to improvements in gasolenc operated rock drilling engines, and

the objects of my invention are: to provide a simple, ligl'it weight, durable gasolene operated rock drilling engine, that embodies various new and practical features which are fully described in the accompanying specification, and which are fully illustrated in the accompanying drawings, in which:

Figure 1, is a front end elevation of my improved rock drilling engine, the supporting shell being omitted. Fig. 2, is a rear end elevation. of the same. Fig. 3, is a vertical, longitudinal, sectional view through the engine. Fig. 4.,is a horizontal, sectional view through. the cylinder casing on the line 4--4 of Fig. 1. Fig. 5, is a plan view of the cylinder casing, the crankcasing being removed. Fig. (i, is a transverse, vertical, sectional view, through a fragment of the cylinder showing the gas inlet, and valve for controlling the same, a coupler being shown in connection therewith, to which a suitable carburcter may be attached. Fig. 7, is a front view of Fig. (i. Fig. 8, is a front View of the valve nipple which screws into the gas inlet.

Fig. l), is a transverse, vertical, sectional view through the cylinder casing, on the line 9 4) of Fig. Fig. 10, is a transverse, vertical, sectional view on the line lll0 of Fig. 5. Fig. 11, is a plan view partially in section, of the fly wheel, actuating arm and buffer springs interposed between the ends of the arm, and projecting lugs on the rim of the wheel, the view being taken from the under side. Fig. 12, is a side view of the wheel-actuating arm shown in Fig. 1 1. Fig. 13, is-a top plan view of the cushioning cap,

- which is mounted on the forward end of the iiston. Fi 14 is a front elevation of the same. Fig. .15, is a rear elevation of the same. Fig. 16, is a rear view of the piston. Figs 17 and .18 are respectively front and rear views oi the drill chuck, the ratchet sleeve being shown in connection with the latter view. Fig. 18), is an elevation of the pawl-ring. nnd Fig. 20, is a view showing the hose connection between the drill bit and the water ('hnnncl ol' the drill.

Similar letters Of reference refer'to similar parts throughout the several views.

lteferring to the accompanying drawings, the numeral 1, designates the cylinder casing of my im roved drill 2, the crank shaft casing, whic is provided with a hub 3. This crank shaft casing is secured by cap screws 4 above an opening'formed in the top of the cylinder caslng. 5, desigates the front cylinder head, which is bolted to the front end of the cylinder casing by bolts 6. The cylinder shell is rovided' with a depending lug portion 7, having a central bore 8, in which is secured the usual threaded sleeve, through which the operating feed screw passes, but the sleeve,

feed screw and supporting shell, in which the drilling engine slides, are omitted, as they are of the type in-general use, and form no part of my present invention. The bottom of the cylinder casing is provided with-slideway lugs 9, which. move in the guideways formed in the sides of a supporting shell, and the drilling engine is moved forward or backward in the shell, by turning the feed screw, as is fully uinlerstood.

The cylinder casing is provided with a cylinder bore 10, in which a piston 11 is reciprocally fitted, and which provided at intervals with packing rings as shown, which are adapted to prevent the explosive mixture which enters the cylinder and crank chamber on, the back stroke of the: piston, from flowing past the piston into the rear end of the cylinder, also to prevent the exploded gas from escaping around the piston to the forward end of the cylinder. The rear end of the cylinder easing forms the explosion chamber of the cylinder, and the peripheral surface of this end of the casing is formed into fluted or ribbed surfzuzes, or thin projecting circum'leren tial flanges, that form heat radiating surfaces, and a threaded aperture 12 is formed through the axial center of the rear end of the cylinder, which receives a plug 13,

having a thrcai'led bore 14, into which a spark plug 15 of the usual type is screwed. The aperture 12 is large enough to receive a finishing tool, such as would be required in finishing the interior surface of the cylinder,

and the plug 13 forms a reducer, to receive the spark plug.

The front en'd'o'l' the piston 11 is provided with a cap 16, which extends orer the end of thepiston for a short :lisinnre; This cap is provided with a forward projection 17. in the coiled springs 27, which are inserted in holes upperside of which a slideway 18 is formed, in which a box 19 of bronze or brass or other suitable metal is fitted. This box is adapted to reccive'a crank pin 20, which is secured to a disk 2], formed on the inner end {if a. shaft 22, which is rotatably n'iounted in an. antifriction journal bushing 23, in the hub of the crank casing. This j urnal lining is novided at itsouter end with a flange 24, w ich bears against the end of the hub of the crank casing, and in the inner end of the crank casing a circul'n ferential recess 25 is formed, which surrounds the end of the lining, and in this recess I place a packing ring 26, which is held against the adjacent face of the disk by 28, drilled into the casing from the bottom of the rescss in which the packing ring is placed. This packing ring is pinned or otherwise held against axial i'novement, and

is adapted to bear against the crank disk and prevent the gas in the cylinder from escaping out through the crank shaft bearing to the atmosphere.

The shaft 22 extends beyond the end of the hub portion of the casing, and terminates in a reduced shouldered portion, upon which. a lly wheel 29 is rotatably mounted so as to rest upon the shoulder. This reduced end of the shaft extends through the fly wheel and is threaded, and a nut 3!) is screwed upon the end of the shaft against the fly wheel, and holds it in'place. A set screw 31 is screwed into the nut, and is adapted to bear against a piece of lead, which contacts, with 'the threaded portion of the shaft to lockthe nut thereon against accidental dis 'ilacement. 'lhrough the fly wheel adjacentto the nut, apertures 32 are formed, to receive ,a suitable spanner wrench, which is used to rotate the fly wheel and crank shaft to start the piston and cause an ex losion in the cylinder. The under side 0 the fly wheel is recessed, thereby forming a depending marginal rim .33 around the wheel, within which is located a fly wheel actuating arm 34, whichis keyed or otherwise secured to the shaft between the fly wheel and the flanged end of the shaft bushing 23. A short hub 35 is formed on the under side of the arm adjacent to the bushing, upon which an insulating ring-36 issecured, and a contact stri is secured to the insulated ring by screws as shown. An axially movable ring 38, is mounted on the flan e of the bushing 23, and on a reduced shou dered portion formed on the end of the hub of the crank casing, allll an insulating plate 39 of suitable substance is secured to this ring, upon which a pair of brushes 40 and 41 are secured, in position to engage the contact strip on the insulatml ring 256, of the arm 34, as the shaft revolves. A circuit wi e 2 is connected to the brush 4H, and a circuit wire 43 is connect ed to the brush 41, and these wires extend to a terminal coupler, secured upon a convenient portion of the cylinder casing, which also connects with a wire leading to the spark plug, and with a battery. and spark coil (not shown), so that a circuit is formed, and a spark produced when the strip 37 contacts with the brushes 40 and 4]. The actuating arm 34, extends on each side of the shaft, to within a short distance of the wheel rim 33, and upon its ends are formed heads 44, hav- 7s ing faces which incline toward the arm at an angle of forty-five degrees. Each head has two faces, as shown, and a threaded a erture 45 is formed in each face, in whie is screwed a stud 46. The outer ends of these studs are formed into short spiral thread portions, that are adapted to receive the ends of cushioningsprings 47, the. coils of which are arranged to screw upon the threaded ends of the studs. Upon diametrically opposite 'sides of the inner periphery of the wheel rim 33, and on a line at right angles to the heads 44, of the actuating arm, are in wardly projecting lugs 48, which are V- shaped and are arranged so that'each of their faces will stand parallel with the opposing face of one of the heads 44 of the actuating Apertures 49 extend from the facesof the lugs through the rim of .the wheel, the apertures in each lug crossing each other at right angles as shown, and in each of these apertures I place a stud 50, which studs are secured therein by ins 51, which extend through the lugs and through the shanks of the studs. The outer ends of these studs are formed with spirally arranged threads adapted to receive the opposite ends of the spring 47; consequently the actuating arm when inoperative stands at right angles to the lugs 48, as shown in Fig. 11, and when rotated -by the rotary motion of the shaft it rotates the fly wheel through the medium of the four cushioning springs 47. The fly wheel and actuatingarm act as a resilient compensating device for the variable reciprocal no movement of the piston when it reverses the direction of its forward stroke and starts on its backward stroke relative to the fixed rotative movement of the crank pin in the box, of the piston, will be fully explainedhereinafter.

Through the axial center of the shaft, I form an oil passage 52, the upper portion of which is enlarged to form a grease cup, and is also threaded to receive a removable cap 53. An oil passage 54 'is formed through the crank disk from its periphery to its center, where it intersects the oil passage,inthe shaft, and a vertical oil passage 55 is formed partially through the crank pin intersecting the oil hole passage of the crank disk, and

- being intersected by a horizontal oil passage 56, at its lower end. Consequently the oil or grease can work from. the grease or oil cup through the-shaft and crank diskto the outside of the crank pin, and thus lubricate the sliding b01119, and the slideway 18 of the piston cap 16. The piston is provided with a hammer bar 57, which. passes. through an aperture in the cap 16, and is secured in a bore formed in the piston slightly below its axial center, when the drilling engine is standing in its normal horizontal position, as illustrated in F ig. 3. This hammer-bar is provided with a collar 58, which is flush with the outer end of the slideway projection 17 of the cap 16, and. between this collar and the cap I place on. the hammer bar a coiled spring 59. The inner end of the cap is in the form ol 8. short sleeve, which fits over the reduced forward end of the piston, so to have a short 'sliding movementthereon, and an air inlet slot 60 is formed thrmlgh this sleeve about I midway of its length, which permits the gasolene air mixture to How into the space between the cap and the end oi the piston, in a manner and for a purpose wluch I will presently describe.

The surface ol' the hammer bar beyond the collar 58, is rifled or provided with spirally arranged teeth 61, as shown in Fig. 3, and this rifled end of the hammer bar extends into a rifled nut 62, which is rotatably mounted in the cylinder head 5. An annular recess is formed in the cylinder head, surrounding the inner end of the rilled nut 62, and this end of the nut is reduced and threaded, and a buffer ring 63 is screwed upon this reduced end of this ritile nut and his loosely in the aunular recess formed in the cylinder head. The opposite end ol this rilled nut is larger in diameter than the cylinder andlits in an enlarged shouldered counterbore l'orined in the cylinder head, and beyond this enlarged portion it is formed with an enlarged collar portion 64, that extends beyond the end ol the cylinder head and bears against it, and the lace of this collar portion which is adjacent to the end ol the cylinder head is provided with a circun'il'erential recess 65, .in which a packing ring 66 is placed, which is pinned or otherwise held against rotation in the collar, and in the bottom oi this recess a number ol' aperturesare drilled, in which coiled expansion springs 67 are placed, which are arranged 1 to hold the packing ring under resilient pres- ,sure against the end of the cylinder head, andprevent the escape of the explosive gas between the rilled nut and the cylinder head. The projecting hub portion of the cylinder head is cxteriorly threaded, and 'a sleeve 68 is threaded to it; which projects loosely over and beyond the rilled nut, and a drill bit holding chuck (if). is rotatably mounted with-- in it. The axial bore of the sleeve is termed in two diameters, the larger of which surrounds the adjaeent end of the rilled nut. This enlarged diameter of the bore ol the sleeve surrounds an enlarged end portion of turned when it sleeve surrounds a reduced portion on the drill chuck, a shoulder 70 being formed at the junction of the two diameters of the drill chuck, which its against a corresponding shoulder 71 formed at the junction of the two bores of the sleeve. The drill chuck extends through and beyond the sleeve a short distance, and this projecting end portion is reduced in diameter, and is exteriorly threaded, and a cap 72 is threaded to it. The drill chuck has an axial hole through it, of the same diameter as the smaller bore of the rifle nut and in alinement with it. Between the opposing ends ol' the rifled nut and of the chuck, a pawl supporting ring 73 is placed. This pawl supporting ring is secured by pins to the adjacent end of the drill chuck, and is provided with three apertures 74, which extend through it and are'adaptml to receive the trul'inions ol' three. ratcl'iet pawls 75. The body portions of the pawls lie in recesses formed in the adjacent end oi the drill chuck, and engage ratchet teeth 76, formed on a sleeve 77, one end of which is threaded and screws into a threaded counter-borev formed in the forward'end oi' the rilled nut, while its opposite. end fits rotatably in a countmbore formed in the drill chuck. The trunnions ol' the pawls also extend pivotally into bearing apertures 78, lormed in drill chuck, which i are arranged opposite to the apertures in -the pawl ring. Expansion springs 79 hold the pawls in engagement with the ratchet teeth 76.

The sleeve 77 has an axial bore ol' two diameters arranged in axial alinenient with the rilled nut and hamn'ler-bar. The smaller bore of this sleeve is made large enough to permit the rilled end 01' the hammer bar to reciprocate loosely in it, while the larger bore extends into the sleeve from its lorward end and terminates in a shoulder at its junction "with the smaller bore, and a striking block 80 islooselymounted inthisei'ilargedbore in the path ol' the hammer-bar, and is prevented from being driven l'orward out ol' the sleeveby a shoulder 81, at the l'orward end of the sleeve, formed by the smaller bore ol" the drill chuck, the bloclcbcing l'ree to move. in the bore in the sleeve. The axial bore in the drill chuck is adapted to receive the shank end of a drill bit 82, which is provided with projecting lugs 83 that are adapted to lit into oppositely arranged concentric recesses 84,

formed in opposite sides of the l'mward end of the drill chuck. These recesses are enough larger than the lugs to receive them loosely, and they extend conceiitrieally around the axial bore of the drill chuck far enough to permitthe lugs to be turned to one side against the end of the recess, and as the drill bit is turned by the chuck in the oppositedirection from the direction in which it is is inserted in the chuck it natthe drill chuck, and the smaller bore of the l urally remains against the ends of the recesses, and is prevented from working out of these recesses by the end of the cap 72, which has an opening 85 large enough to receive the shank and lugs of the drill bit, the drill bit being turned when inserted in the chuck so that the lugs will be out of line with the opening 85; consequently when the drill bit is inserted through the cap into the chuck, and its lugs are turned to one side against the ends of the recesses 84, it can not be withdrawn or accidentally work out, the lugs are covered by the end portion of the cap.

The cylinder casing has formed on one side an enlargei'nent 86, concentric with the axis of the casing, which extends from the forward end of the casing about two-thirds of its length. This enlargement begins substantially at a point determined by a line drawn vertically through the axial center of the casing, and extends around and terminates slightly above/a point determined by a line drawn horizontally through the axial center of the casing. A port 87 is formed in the enlargement 86, which extends from a point substantially coincident with limit of forward movement of the forward end of the piston cap, to a point substantially coincident with the limit of forward movement of the rear end of the piston. The upper half of the forward portion of the cylinder is enlarged, shown in Figs. 5 and 9 to accommodate the siideway projection 17 on the piston cap 16, and slideways 88 having vertical and horizontal faces, are formed on each side of this enlarged portion of the cylinder, upon the horizontal faces of which slide the ends of the projection 17, as the piston reciprocates, while dcpeinling guide lugs 1.6" fit between the vertical faces of the slideways.

The port 87 opens into the enlarged end of the cylinder through one of these slideways, but beyond the end of the projection 17, so asnot to be obstructed thereby, and this enlargen'ient of the upper half of the cylinder is extended far enough rearward to accommodate the slideway projection 17, when the piston is at the limit of its rearward movement. At the forward end of'the port there are openings 89, extending from the port through the shell of the cylinder, and the port opens into the rear end of the cylinder by means ofsimilar openings 90.

Centrally of the forward or enlarged portion of the cylinder, and on that side upon which enlargement 86 is formed, is located an interiorly threaded hub 91, into which is screwed one end of a valve nipple 92, the inner end of which is formedwith a valve seat. A guide tube 93 is formed within the nipple,

being connected to the nipple by integral webs 94, shown in Fig. 8, and through this tube extends the stem 95 of a val ve 06, which normally rests against the seat in the end of the valvenipple. A disk secured upon the outer, end of the stem, and a coil spring 97 is 'erture 106 is formed in the sleeve 68,

interposed between the disk and the Webs 94, to hold the valve against its seat. The outer end of the valve sleeve has a circumferential groove 98, and a sleeve 99 is mounted on the nipple, so as to rotate freely thereon, being held upon the nipple by a spring dog 100, which projects through an opening in the sleeve, and into the circumferential groove of the nipple. To this sleeve is connected a carbureter and gasolene tank, the arrangement and construction of which are neither illustrated nor described in this application; as it is fully set forth in an ap plication for gasolene operated rock drilling engines, filed by me on the 4th day of September, 1906, and again more fully set forth v in an application for detachable carbureten for gas operated rock drilling engines, filed by me on the 15th day of October, 1906, Serial No. 333,279, the arrangement of the tank and carburetor forming no part of my present invention.

At a point diametrically opposite to where the port 87 enters the rear end of the cylinder, are exhaust ports 101, which open into a fine 102, formed integral with the cylinder casing. The forward edges of these ports are in line while the exhaust port extends slightly farther. to the rearward. A hood 103 sur rounds this end of the casing, and is provided with an outlet 104, in line with the flue 102, and to a hub 105 surrounding this outlet, may be coupled a suitable hose (not shown) by which the exhaust may be conveyed away from the cylinder to any desired point.

A circumferential groove or channel is formed in the chuck 60, and a threaded ap- Which aperture opens into the channel105". A passage 107 extends from thechannel t0 the forward end of the chuck, and throu h the cap 72. Water is admitted through t e aperture 106, to the channel 105", whence'it passes out through the passage 107. The drill bit is hollow from its cutting end, to a 1 point which will be adjacent to the end of the chuck, when the drill is inserted in the chuck, I and an aperture is formed in the side of the drill, communicating with the hollowbore.

A short section of hose 108 connects the 3 5 chuck passage 107 with the aperture in the side of the drill, being attached'to the drill by any suitable style of coupler, and thus water is admitted to the drill. The hose can not become twisted, as it moves with the chuck and drill.

The operation of the improved drilling engine is as follows: The fiy'wheel is first turned manually to give the initial movement to the piston, and as the piston recedes, 12; gas from a suitable-carburetor is drawn into the forward end of the cylinder, through the valve nipple 02,and is forced into the rear end of the cylinder through the port 87, by the forward stroke of the piston; as the pleting a circuit between a battery, sparkeoil, cylinder, and the spark plug 15, causing a spark, which explodes the gas and throws the piston and hammer bar forward. This movement of the piston will be transmitted to. the fly wheel, through the medium of the cushioning'cap 16, having the slideway 18 in whichthe crank pin box 19 moves, which carries the crank pin with it, thus turning the shaft 22, and actuating arm 34, which turns the fly wheel through the mediumof the springs 47. As the hammer bar nears the end of its stroke, it'will strike the block 80, located in the ratchet .sleeve, through which its blow will be communicated to the end .ofthe drill bit. It will be'noted that this block is provided with suitable packing rings, to prevent the escape of gas from the cylinder. Should the hammer bar and block strike the drill before the crank pin reaches the dead center line, the piston will be brought to a stand still, but the crank .pin will continue around carrying with it the cushioning cap 16, which will be moved away from the end of the piston. Its sleeve end however, will not become disconnected from the piston, and when the slot 60 in the sleeve passes the end of the piston, the gas in theforward end of the cylinder will be drawnthrough the said slot into the s ace. between the front end of the piston ant the cap, and as the momentum imparted to the wheel .by the explosion carries the crank pin past thedead center line, the cap 16 will slide back again on the end of the piston,

but the gas between the piston and cap will cushion the return stro e of the crank pin and the contact of the cap with the end bridge 111.

of the piston, thus reducing the strain and jar upon the crank pin, shaft, and fly wheel, to a minimum, the springs 47 connecting :the actuating arm and fly wheel also contributing to this result. The spring 59 on the hammer bar, willcushion excessive forward movement of the cap 16, as in case'of a missed explosion at full speed or when gas is shut ofl'suddenly, and should the drill strike a fault and permit the piston to be, thrown to the limit of its stroke, the fly wheel will then take the shock of the return movement of the crank and thus prevent injury or breaking of the parts. The gas )assin into the ex losion end of the c lin- 1 der, will be deflected toward its rear end by a'dcllecting surface 109, formed on the end of the piston, as shown in Fig. 16, and the port 101 by a similar deflecting surface 110,

and these two surfaces are separated by a "li e rifled nut 62 turns the [,POI'UODSO engine, a cylinder, a piston in said-cylinder,

a gas explosive chamber in which said piston reciprocates,'an electric spark igniting apparatus operatively connected to said cylinder, there being a valve controlled explosive gas inlet port extending along the central portion of said cylinder to the opposite end portions ofsaidcylinder, a rock-cutting drill-bit arranged in said cylinder in striking relation to said piston, means including a crank shaft,

and a fly wheel arranged with a resilient oscillating movement independent of said crank shaft for moving said piston onits rearward strokes.

2. In a gasolene gas explosion rock-drilling engine, a gasolene gas explosion cylinder, a-

piston reciprocally mounted in said cylinder, there being a valve controlled gas inlet port leading into said cylinder in front of said piston and connected to a supply of gasolene air-gas, and a port in saidcylinder leading from its front portion to the rear end portion of said cylinder, a crank shaft arranged to be driven by said piston on said pistons forward stroke and adapted to drive said piston on its rear stroke, a fly 'wheel and means whereby said fly wheel is connected to said crank shaft in such a manner as to have a short predetermined resilient independent movement on said crank shaft.

3. In a gasolene gas explosion rock-drillingv engine, a gas explosioncylin-Ller, a piston reciprocally mounted in said cylinder, a rockcutting drill-bit mounted in said cylinder in the reciprocal path of said piston, a striking block arranged between said drill-bit and said piston adapted to be struck by it, and to impart its blow to said drill-bit, there being a port connected to a supply of gasolene air-gas, and extending to the opposite ends of said cylinder, a rotative crank-pin. and shaft mounted in said cylinder and arranged to operate said piston on its rearward stroke, and an electrical spark gas igniting apparatus operatively connected to said cylinder and said crank, and arranged to ignite a supply of gas in said cylinder at a predetermined point of said pistons movement.

4. In a gasolene gas-explosion operated rock-drilling engine, a gas explosion cylinder, a drill-bit striking iston-hammer reciprocally mounted in said cylinder, a rock-cut ting drill-bit'supported by said cylinder in.

the reciprocal pat i ofsaid piston, there being a gas in said cylinderand arranged to be etfport extending to the opposite end controlled by the reciprocal movements of said piston, a crank shaft and crank pin'arranged in said cylinder to Operate said piston in one direction of its movement, an arm connected to said shaft, a fly wheel mounted loosely on said shaft and means for resili ently connecting the fly-wheel with said arm, and an electrical .spark device in circuit with said gas explosion cylinder and arm.

5. In a gas explosion operatedrock-drilling engine, the combination of a gas explosive cylinder and a drill-bit striking hammer piston reciprocal in said cylinder, a rotative drill-bit supported in said cylinder in the striking path of said piston, a striking block between said drill-bit and piston, there being ports arranged to be controlled by the reciprocative strokes of said piston for admitting a supply of gas to said cylinder, and an electrical spark producing apparatus for igniting the gas in said cylinder at a predetermined point' of the rear stroke of the'piston.

6. In a gas explosion operated rock-drilling engine, the combination of a cylinder, a reciprocating p ston, a rotative drill-bit, and a striking block between said drill-bit and piston, wi h a rotative fly-wheel arm, crank shaft, crank pin, and a fly wheel mounted on said shaft, springs arranged to connect said arm and fly Wheel, an electrical. gap spark apparatus, and means for rotating sa1d drill-bit.

7. In a gas explosion operated rock-drilling engine, the combination of a gas explosion cylinder arranged to receive gas from a source of supply,'a drill-bit-striking hammer piston. reciprocally mounted in said cylinder, there being ports in said. cylinder for leading said explosive gas in front of said piston whence it is driven to the rear end of the cylirnler by the forward stroke of the piston, means including an electrical intermittent spark-producing device for igniting said-gas at a predetermined point of said pistons reciprocative movement to drive said piston against said drill-bit, andmeans connected with and actuated by said piston including a crank. shaft, a crank pin, a fly wheel and operating arm, and a cushioning device on t 1c end of said. piston, for operating it on its rearward or inoperative stroke.

8. In a gas explosion operated rock-drilling engine, a cylinder provided with a gas. explosion and a gas compressing end, and having a port extending adjacent to the said ends, connected with a valve controlled inlet, a hammer piston reciprocally mounted in said. eylinder,which draws gasinto the forward end of the cylinder on its rearward stroke, and forces it into the rear end of the cylinder on its forward stroke, means for igniting said gas at a predetermined point of the stroke of said plston, a sliding buffer cap on the forward end of said piston, having an inlet to admit air between said capand the end of the piston, when the cap is moved forward, and means including a rotating crank pin arranged to engage said cap for moving said piston ,on its rearward ing engine, the combination of a cylinder and a piston, of a crank casing connected to said cylinder, a crank shaft rotatably mounted in said casing, a crankin on'the inner end of said crank shaft, a sliding cap on the front end of said piston having a sleeve thereon provided with an aperture arranged to admit the explosive gas between said cap and the front end of said piston, whereby to form a cushion between the two, a slideway in said sleeve arranged transversely to its movement, a journal box slidably mounted in said slideway and journaled to said crank pin, a drill-bit driving hammer bar connected to said piston below its axialcenter and extend ing through said cap, a collar on said hammer bar a short distance from the front end of said. sleeve, a coiled. spring. on said hammer bar between said collar and said sleeve, anda fly wheel mounted on said crank shaft.

10. In a gas explosion rock-drilling engine, the combination with a cylinder, of a piston reciprocally mounted therein, the forward movement of which is accomplished by an explosion of gas, a reciprocating cap mounted on the forward end of said piston having an-inlet therein adapted to admit the explosivc fluid of said cylinder between said-cap and the front end of said piston, a sliding ournal box mounted 1n sa1d cap, means including a crank shaft connected to said. journal box for moving said piston throughout its rearward stroke, a drill-bit driving hammer bar extending forward from said piston and extending through said ca an abutment on said hammer bar and a resilient member between said abutment and said ca '11. In a gas explosion operated rock-dril ing engine, a cylinder, a piston in said cylin der, a sliding cushioning cap on the front end of said cylinder, a sliding journal box in said cap, a crank shaft and. pin connected to said sliding journal .box, a fly wheel resiliently connected to a driving arm mounted on said crank shaft, a drill driving hammer bar connected to said piston and, projecting through said sleeve, an abutment on said hammer bar,

a coiled spring between said abutment and said sleeve, a rifled surface on said hammer bar, a pawl and rate at controlled rifled nut mer piston reciprocally mounted insaid cylinder, said cylinder having a port controlled by said piston, through which gas is forced by said piston to the rear end of said cylinder, an electric spark device and apparatus arranged to ignite said explosive to operate said piston on the forward strokes of its reciprocal movement, a iiywheel crank shaft rotatably mounted in said cylinder in the path of the forward stroke of said piston and arranged and adapted through the medium of its rotative momentum to move said piston on its rearward or backvard stroke, a rotative rock-cutting drillbit supported in the recipro'calpath of said piston, and a striking block between said drill-bit and said hammer piston. 1

13. In a gas explosion operated rock-drilling engine, the combination with a cylinder haviiig a crank chamber, and a piston, provided with a cushioning recipioeating cap, a sliding box in said cap, a hammer bar and a spring between said hammer bar and said ,cap, of a crank sh aft in said crank chamber, a

fly-wheel on the outer end of said shaft, a crank disk ".1 the inner end of said crank shaft in saie crank chamber, and the crank pin rotatably secured to the sliding box of the cap.

14. In a gas explosion rock-drilling engine, a gas explosion cylinder, comprising a cylindrical portion having a drill-bit holding chuck at one end a rock-cutting drill-bit rotatably mounted in said chuck, a rifledsleeve rotatably mounted in said cylinder adjacent to said chuck, a hammer piston reciprocally mounted in said cylinder to strike said drill-' bit, a crank shaft and crank pin operated by the forward stroke of the piston for moving said piston rearward, means including a reciprocating cap connected to said piston for cushioning the rearward. movement of said crank pin, means connected with said piston and rifled sleeve and chuck for rotating said drill-bit step by step, said cylinder having an explosion chamber at its rear end provided with a corrugated peripheral surface and having a port connecting its forward and rear-ends, and connected with a valve controlled inlet, said piston acting to draw into the forward end of the cylinder on its rear stroke, and force it through. said port to the rear end of the cylinder, on its forward stroke, and means for igniting said gas at a predetermined point of said pistons stroke.

15. In a gas explosion operated rock-drilling engine, the combination with a cylinder and a piston, said cylinder having a gas inlet leading into it, in frontof said piston, of a nipple threaded to said inlet, having a valve seat, a valve disk arranged to lit said valve seat, .a valve stem on said valve disk, a support for said valve stem in said nipple, a spring arranged between said support and the front end of said cylinderby the suction action of the rearward stroke of said piston, there being a gas port extending from the front end portion of said cylinder to its rear end portion, packingrings around said piston for preventing the escape of gas around said piston on either stroke, means including an electrical sparking device for igniting said gas at a predetermined part of the reciprocal stroke of said piston to drive it on its forward stroke, a reciprocating air cushioning cap on the front end of said piston provided with a reciprocating journal box, and means including a fly-wheel crank and crank pin coi'iperatively connected to said piston cap journal box for moving said piston on its backward stroke, rotative rock cutting drill-bit arranged in said cylinder in the reciprocal pathof said piston, and a striking block between said drillbit and said piston.

16. In a gas explosion operated rock-drilling engine, the combimition of the cylinder having a gas inlet port, a valve in said port, a piston reciprocating in said cylinder and arranged to control said port and to open said valve by the suction of i ts rearward stroke, a reciprocative cap on said piston, a journal box in said cap, a crank shaft and crank pin arranged to be in operative engagement with said journal box, an arm secured to said crank shaft, a fly wheel mounted on said crank shaft and arranged to surround said arm, and coiled springs on the opposite sides of the opposite ends of said arm and positioned between said arm'and said fly wheel, and arranged to connect said lly wheel with resilient connections to the opposite sides of each end ofsaid arm.

17. In a rock-drilling engine of the character described, the combination of a cylinder and a piston, a cushioning cap on said piston, and a sliding box in said cap, with a crank pin in engagement with said box, a crank shaft, an arm secured to said crank shaft,

and a fly wheel resiliently connected to said.

arm.

18. In a gasolene operated rock'drilling engine, the combination of the cylinder and the crank shaft, having an arm secured thereto, a fly wheel mounted loosely on said crank shaft provided with a peripheral rim arranged to surround he opposite ends of said arm, threaded plugs connected to the opposite sides of both ends of said arm, abutments on the inner peripheral rim of said fly Wheel, threaded plugs connected to said abutments and arranged opposite to the threaded abutments on said arm, and coiled springs threaded at one end to the threaded ends of said plugs of both sides of the opposite ends .of said arm and threaded at their opposite qion being formed between the cap and the end of the piston when the cap is moved so as to form a space between it and the end of the piston; I 7

20. In a rock-drillin engine of the character described, the com ination with a cylinder of a reciprocating piston having a hampiston and mer bar fitted in an aperture therein; 'a cap having a sliding movement on the end of the provided with an air inlet; a crank shaft having a fly wheel mounted resiliently thereon, and a crank pin on said shaft connected with said cap, which slides said cap on the end of the piston omits forward movement, thereby admitting air between the cap and the end of the piston, which forms a cushion when the cap is returned by the return movement of the crank pin.

' 21. In a rock drilling engine of the characsaid crank shaft,

sea??? ter described, the combination with a cylin der having an explosion chamber at one end, a reciprocating hammer piston in said cylinder, and a cushioning device upon the forward end of said hammer piston, of a shaft mounted in said cylinder at right angles to said piston, a fly wheel on the outer end of a crank disk at the inner end of said shaft, a crank pin on said crank disk which engages said. cushioning device, said piston being thrown forward by an explosion of gas, thereby rotating the shaft and its disk and pin and fly wheel, which returns the piston on its rearward stroke.

22. In a rock-drilling engine of the character described, a cylinder having a valve controlled inlet connecting with a port which communicates with the cylinder adjacent to its ends; ahammer piston in said cylinder having an air cushion cap on its forward end; a crank shaft having a crank pin engaging said cushion cap; a fly wheel resiliently mounted on said shaft, and a spark device connecting said wheel and cylinder.

In testimony whereof I allix my signature in presence of two witnesses.

G. SARGENT ELLIOTT, ADELLA M. Fowiln. 

